An 88 S-10 behind a 2.5 L4 is geared 3.76,2.18,1.41,1:1 and .72 and as pointed out, you have to look at the speedo hookup. The mechanical will have a fitting to accept a conventional speedo cable.
If you already have the foot starter and a 6 volt starter you will need the transmission and driveshaft with front yoke. Your clutch disc will be a RCF-4201 (10")and you can use your old pressure plate if it's in good shape. A new stock throwout bearing is recommended as well as a new pilot bushing in the crank.
You might check out a couple pics in my album that will help you with the install and eliminate clutch drag.
There is a wealth of good info out there (and also some questionable) so make sure your sources have actually done the conversion and are driving the vehicle. Hope this helps.
